macos: disable bulkstat

macos: disable bulkstat

1.6 only change. there's still an issue where potentially
multiple contexts reference a vnode which needs to be finalized; the fixup
is successful but there's no hint to other threads to reref before proceeding
(no actual troublesome access while waiting for the fixup as the vnode
will not have actually been CStatd yet)

Change-Id: Ib72f69b74c94b7cac74a9a01a54a8872e32f9717
Reviewed-on: http://gerrit.openafs.org/4717
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>